os of system fetching port source

[qjail1]

My port has it's source hosted on sourceforge.net. That site has 
function that shows the count of times the port source file has been 
downloaded along with the country and operating system type of the 
computer requesting the download. 99.9% of the time the operating system 
is "unknown". I can only assume those are downloads originating from 
FreeBSD systems using the "make install" method. I believe the port 
system uses a fetch/ftp call to download the ports source file from 
where ever it's hosted at.

Is there some fetch/ftp option to tag the ports system download request 
with the operating system the request is coming from?